There are many cases where a light emitting layer using a gallium nitride (GaN)-based material is formed on a sapphire substrate. In a flip chip mount-type device in which a p-side electrode and an n-side electrode are provided on the side opposite to the extraction surface of the light, the light is extracted from the GaN layer through the sapphire substrate into the air. The refractive indexes of the GaN layer, the sapphire substrate, and the air are 2.4, 1.8, and 1.0, respectively; and the refractive index of the medium changes in stages in the direction in which the light is extracted.
On the other hand, a structure has been proposed in which the sapphire substrate is removed to downsize and reduce the thickness of the device. In such a case, because there is no sapphire substrate, the refractive index of the medium changes greatly in the direction from the GaN layer toward the air; and the light extraction efficiency may decrease.